Adjustable condenser



' Sept. 18, 1928. 1,684,917

| A. HAMMARLUND ADJUSTABLE CONDENS ER Filed Feb. 9, 192"! INVENTOR LloydfLHam drlunaf, ill 7/ (1 am P at'ented Sept. 18, 1928. A

TES

UNI/TED "STA 1 Application fled February a, 1921. Serial Io. iezooa.

My invention relates to a type of condenser which is particularly suited to use as an equalizer, or neutralizer, or balancing condenser.

. One object is to provide a sim 1e inexpensive and reliable construction which can be readily adjusted.

Another of this character which will retain its adjustment. v y

Another obfect is to provide a construction of this character which is compact and can be readily installed and adjusted.

Another object is to' provide a construction of the character described which is inexpensive and can be readily manufactured and assembled according to standard specifications 7 Another object is to provide a condenser of this character which on account of its small size has a minimumstray free electrostatic field to other elements of the circuit.

Another object is to produce a condenser of this character having a small minimum capacity and a comparatively large maximum, thus making it adaptable for use either as a balancing or neutralizing condenser or as a correcting condenser for multiple unit condensers of uni-control receivers.

In its preferred form the invention contemplates a base formed of insulating material and having attached to it one of the plates or electrodes of the condenser. The pther plate or electrode is in the form of a spring plate. This plate is provided with spring legs and is arched so thatas it is drawn toward the other plate the volume of air dielectric between the twoplates "is decreased until the edges of the spring plate touch the solid dielectric and from th s point on the volume of air dielectric is also decreased and the area of contact of the spring plate with the solid dielectric is gradually increased, thus producing a condenser with a small rate of variation of capacity over part of the range of its adjustment and a considerably larger-rate of variation during theremainder of its range. The two plates are provided with lugs which engage the insulating base so as to hold them in their proper positions.

Fig. 1. is a plan view of'a condenser embodymg one form of my invention.

Fig. 2 is an end view of the same.

Fig. 3 is a longitudinal sectional view.

object is to provide a construction Fig. 4 is a dropped perspective or exploded view showing the various parts before assembling.

The base 5 may be formed .of any suitable insulating material, such, for instance, as molded phenolic composition. The stationary plate or electrode 6 may conveniently be stamped of sheet brass and provided with ears or lugs 7 at its opposite sides adapted to be bent so as to extend through openings 8 n the insulating base and be turned over as shown in Fig. 3 so" asto connect the parts securely together. This plate 6 also preferably has an extension 9 serving as a convenient means for attaching the condenser to any suitable support, such as the grid post ofa vacuum. tube socket or a terminal of a variable condenser.

The movable plate or electrode consists of a body'portion 10 with spring legs 11 at each end. The body of the plate is arched or crowned in two planes at right angles to each other and provided with a central passage 12 for the screw 13. The insulating base 5 is provided with a seat 14 for the screw 13. A suit-able dielectric material is interposed between the plate 6 and 10 as, for instance, by the application of a layer of mica or other suitable material 17 on theoutcr surface of theplate 6. The aperture in this dielectric is of such size as to closely embrace the screw 13 and the dielectric may be of such shape as to-be held in position by the legs 11. The aperture 16 in the plate 6 is of sufficient size-to reduce the capacity at this point between the plate 6 and the screw 13 to a very low value.

The pairs of legs 11 are preferably arched in the form ofa semi-elliptic spring whose center is connected to the bod 10 by a neck 18 and whose tips 19 are bent at so as to embrace the edges of the body 5 as shown in Fig. 2. These tips thus prevent the plate 10 from turning on the base when screw 13 is rotated.

One end of the plate 10 is preferably provided with a projecting lug 20 serving as I; convenient means for the attachment of a con ductor.

The comparatively wide spacing between the plate 10 and the spring legs 11 reduces to a low value the capacity between these legs and the plate 6.

The arched or crowned form of the plate 10 and the semi-eliptic spring legs 11 serve to produce a gradual increase in the capacity as the screw is tightened.

I claim: I

1. A variable condenser comprising an insulating base, a stationary flat plate having lugs secured to the base, an arched plate having spring wings embracing the edges of the base, a screw for drawing the two plates toward each other and changing the shape of the arched plate and a dielectric interposed between said plates.

2. A variable condenser comprising an insulating base, a stationary plate secured thereto, a spring plate having arched ends connected to the main portion by narrow necks and having means interlocked with the base to prevent relative rotation and an adjusting member passing through said plates and pressing on the sprlng plate to change its shape relative to the stationary plate.

3. A variable condenser comprising an 1nsulating base having attached thereto a flatconducting plate, a conducting spring plate having two projecting spring wings at each end embracing portions of the base and a central adjusting member and pressing on the spring plate to change its shape.

4. An adjustable condenser consisting of an insulating base, a conducting plate secured thereto by cars integral with said plate, a movable plate having a body portion which, when not under stress, approximates a portion. of a surface of a sphere in shape, two semi-elliptic spring portions attached toand integral with said body portion, said spring portions being bent attheir ends to embrace said insulating base, a dielectric sheet interposed bet-ween said plates and a screw. working in said base so as to exert variable pressures on said body portion, thus varying both the area of contact of said body portion with said dielectric, and the volume of air dielectric between said plates.

5. An adjustable condenser comprising a movable plate of spring material having an arched central portion and two semi-elliptic spring portions attached to and integral with said central portion, a flat stationary plate, a dielectric interposed between said plates, an insulating base embraced by the ends of said spring portions and carrying said stationary plate, and means for varying the av erage distance between said stationary and movable plates.

. 6. An adjustable condenser comprising an insulating support, a plate secured thereto and having a perforation, a movable plate having spring legs integral therewith at opposite edges thereof, an adjusting screw passmg throu h said plates into said support and having a ead pressing on the movable plate to change its shape and a dielectric sheet between said plates, said plates being shaped so that the condenser has a small rate of variation of capacity over a part of the range of the adjustment and a substantially larger rate of variation of capacity over another part of its range of adjustment.

7. An adjustable condenser comprising an insulating .body, a metallic plate secured thereto and having an integral projection adapted to be secured to a support, a reversible spring plate having guide lugs adapted to interlock with the insulating body to prevent relative rotation, said spring plate having a projecting terminal lug at one end adapted to receive a circuit connection, a sheet of dielectric'material between said plates and an adjusting screw for drawing said plates together, said spring plate being reversible end to end whereby its terminal lug may be placed adjacent either end of the insulating body.

8. An adjustable condenser comprising an insulating body, a metallic plate mounted thereon and having a projection adapted to be secured to a support, a reversible spring plate having spring arms adapted to engage the insulating body to prevent relative rotation, said spring plate having a projecting terminal lug at one end adapted to receive a circuit connection, dielectric material between said plates and an adjusting member for drawing said-plates together, said spring plate'bein'g reversible end to end whereby its terminal lug may be pleiced adjacent either end of the insulating bo 9. An adjustable condenser comprising an insulating support, a metal plate mounted thereon and having a perforation, metal plate having spring legs connected therewith by narrow necks at opposite edges thereof and terminating in lugs loosely embracing the edges of the insulating support, an adjusting member passing through said plates into said support and having a head pressing-on the movable plate to change its shape and a dielectric sheet between said plates, said plates being shaped so that the condenser has a small rate of variation of capacityover a part of the range of the adjustment and a substantially larger rate of variation of capacity over another part of its range of adjustment.

10. An adjustable condenser comprising a movable plate of spring material having a main central portion and two semi-elliptic spring portions attached to said central portion by narrow necks, a stationary plate of approximately the same active area as the main central portion of the movable plate, a dielectric interposed between said p ates, an insulating base engaged by the ends of said spring portions and carrying saidstationary plate, and means directly engaging the main central portion of the movable plate for varying the average distance between said stationary and movable plates.

11. An adjustable condenser consisting of a movable an insulating base, a conducting plate secured ends connected to the main portion by narthereto, a movable plate having a body porrow necks and having means interlocked tion which, when not under stress, approxiwith the base to prevent relative rotation and mates a portion of a surface curved in two an adjusting screw passing through said directions, two spring portions attached to plates and having a head pressing directly and integral with said body portion, said on the spring plate for changing its shape. spring portions engaging said insulating 13. A variable condenser comprising an base, a dielectric sheet interposed between insulating base, a stationary fiat plate mountsaid plates and a member working in said ed on the base, an arched plate having spring base so as to exert variable pressure on said wings at its opposite end engaging the edges body portion, vthus varying both the area of of the base and prevented from rotation, a contact of said body portion with said dielecscrew having a head engaging the arched trio, and the volume of air dielectric between plate for drawing the two plates toward each said plates. other and a dielectric interposed between said 12. A variable condenser comprising an plates. insulating base, a stationary fiat plate mount ed thereon, a spring, plate'having yielding LLOYD A. HAMMARLUND. 

